1. Field of the Invention
The present invention relates generally to a steering and positioning structure of a ratchet screwdriver, and more particularly to an innovative one which is adapted to a multi-tooth meshing mechanism for easy forming and demolding.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98.
The ratchet screwdriver is a common handheld tool in everyday life, which is utilized in a unique manner that the screwdriver could be freely rotated positively (or reversely in idle state), reversely (or positively in idle state) or bi-directionally for ease-of-operation and convenience.
As for a conventional steering and positioning structure, a shaft lever with gearing assembled into the main body is used for guided meshing with the help of two □-shaped snappers and two abutting seats vertically inserted into the radial slot of the main body. Of which, the cross frame of said □-shaped snapper can be meshed with the gearing of the shaft lever, and the vertical frame of □-shaped snapper can be extended onto the abutting seat; when the user rotates positively or reversely the bushing sleeved onto the main body, an abutting seat can be pressed to push the corresponding □-shaped snapper, such that the snapper's cross frame is disengaged from the gearing, and another □-shaped snapper is meshed with the gearing for single-way rotation (in idle state it rotated in other direction).
Yet, as □-shaped snappers of the conventional steering and positioning structure are meshed with the gearing of the shaft lever only via the cross frame, insufficient torsion likely exists during rotation of the ratchet screwdriver. To resolve this problem, the gearing of the shaft lever is generally designed with coarse teeth with bigger pitch, so as to increase the meshing contact area of the □-shaped snapper's cross frame and the gearing, and also raise the rotational torsion; however, owing to bigger pitch of the gearing, the meshing, points for meshing rotation will decline when the ratchet screwdriver is used (□-shaped snapper's cross frame is meshed with the gearing only when the ratchet screwdriver is rotated to a specific angle). When space-saving is at a premium, the insufficient space likely causes interference to affect convenient use of the ratchet screwdriver or even causes its unavailability. For this reason, the gearing of the shaft lever is designed with fine teeth with smaller pitch. In such a case, insufficient torsion likely occurs due to single-tooth mating of the □-shaped snapper and the gearing during actual applications. Therefore, them-shaped snapper must be designed with a multi-tooth meshing pattern to increase the rotational torsion. As the □-shaped snapper is generally designed into a plate pattern (by means of punching), multi-tooth pattern could not be formed in the manufacturing process. If powder metallurgy is applied to the forming process, demolding is made impossible due to the □-shaped structure, bringing about big problem in manufacturing.